Exercise, we all know, is fundamental to good health. For dogs and humans alike, slothful ways lead to, at best, diminished well-being and poor muscle tone, at worst obesity, heart ailments, and joint problems. In dogs a couch potato existence can also prompt behavior problems. Sometimes just quirks, sometimes full-on neuroses similar to those seen in caged dogs.

Almost all dogs were bred with a working purpose in mind. The seemingly sedate Basset Hound? Bred for rabbit hunting. The Corgi? A herder. It makes sense, then, that all dogs need to run their engine, whatever its size, frequently and vigorously to function well. (And contrary to popular belief, dogs rarely self-exercise if left alone outside. They stalk birds, bark at strangers, and lie around in the shade.)

Exercise earns you a happier, better-behaved dog. Tired dogs bark less, chew less, sleep more, and rest easier when left home alone. And exercise has profound effects on a dog’s personality. The same dog can either tear through the trash and disembowel the couch cushions or snooze peacefully, depending on the quality of the workouts he gets.

So, must you take up marathon running if you have a Border Collie or a terrier mix? Of course not. But a stroll around the block is not enough. Train your dog to fetch or play Frisbee. Sign up for a dog sport or activity like tracking, flyball, or agility. Let your dog play with other dogs regularly. And if life is too busy, consider hiring a dog walker, or, if your dog enjoys the company of other dogs, send him to doggie day care.

Knowing you’ve upheld your end of the bargain as a loving guardian, that’s healthy, too.